The first advertisements will begin appearing in Pennsylvania against Republican Sen. Patrick J. Toomey on Facebook , Twitter and the massive Google ad network used by many websites. “The Republican agenda puts special interests and partisan ideology ahead of what’s best for everyday Americans and Pat Toomey is the poster boy for those misplaced priorities,” said Shripal Shah, a spokesman for Senate Majority PAC.

The Pennsylvania digital ads — the first installment in the group's 2016 digital effort — ask, "Who's Pat Toomey Really Working For?" and link to a report that accuses him of voting along the lines of one of the Democrats' favorite boogeymen — the billionaire Koch brothers.

Steve Kelly, a spokesman for Toomey's campaign, took issue with that depiction.

“The Allentown Morning Call said it well when it wrote, 'Pat Toomey puts principles over party-line obedience'– whether it’s on background checks for gun purchases, job creation, or keeping predators out of schools, Pat is proud of his work across party lines to make our communities safer and our economy stronger," Kelly said. "Suggestions to the contrary are nothing but election season political attacks.”